Type 1 diabetes mellitus (T1DM) is one of the most common chronic diseases in children that may be complicated by micro or macrovascular complications. Measurement of the carotid intima-media thickness (CIMT) allows the early detection of atherosclerotic alterations of blood vessels that may complicate T1DM. This study is a case-control study. Participants were classified into two groups. The first group included 40 children with T1DM and the second group included 30 matched healthy controls. The studied cases were recruited from Endocrinology and Diabetology Unit, Pediatric Hospital, Ain Shams University. Serum apelin, cholesterol, TG, LDL were measured for every case. Also, albumin level was analyzed in urine. Measurement of the carotid intima-media thickness (CIMT) was done for all cases. Comparison between T1DM patients and controls revealed that serum apelin, cholesterol, TG, LDL and albuminuria were significantly increased in cases compared to controls. Significant positive correlations were detected between HbA1C, albuminuria and lipid profile with apelin in the diabetic group (p < 0.05). CIMT has significant positive correlation with serum apelin levels (r = 0.36, p = 0.05). Also, this study found positive correlations between CIMT and some variables as LDL, SBP z-score and duration of the illness. Increased levels of serum apelin in T1DM patients may be considered as predicting factor for the ongoing development of vascular sequels. This study highlighted the possible validity of apelin assay as an early predictor of atherosclerosis in T1DM children. Evaluating CIMT in these patients is of at most important for early detection of subclinical atherosclerosis.